Apparatus for fabricating sheet metal joints



E. c. FRAZE 3,196,817

APPARATUS FOR FABRICATING SHEET METAL JOINTS July 27, 1965 15Sheets-'-Sheet 1 Filed Oct. 30, 1962 July 27, 1965 E. c. FRAZE 7APPARATUS FOR FABRICATING SHEET METAL JOINTS Filed 001:. 30, 1962 15Sheets-Sheet 2 Ema M. CLEO TTORNEYS RAZE y 1965 E. c. FRAZE EJQfilAPPARATUS FORFABRICATING SHEET METAL JOINTS Filed 001:. 30, 1962 15Sheets-Sheet 3 I T 1% 1 1 LQ' 2 INVEN TOR. Emmu Luau YRfim E. c. FRAZE3,196,817

APPARATUS FOR FABRICATING SHEET METAL JOINTS July 27, 1965 15Sheets-Sheet 4 Filed 001:. 30, 1962 INVENTOR.

Cm YER LL 6% July 27, 1965 E. c. FRAZE 9 APPARATUS FOR FABRICATING SHEETMETAL JOINTS Filed Oct. 30, 1962 15 Sheets-Sheet 5 23 2. 5% INVENTOR.

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APPARATUS FOR FABRICATING SHEET METAL JOINTS FRAZE l5 Sheets-Sheet 7Filed Oct 30, 1962 INVENTOR. Cum 1mm wwumu@m III ,3 BY ZQS Jmfly 27,1965 E. c. FRAZE 9 3 APPARATUS FOR FABRICATING SHEET METAL JOINTS FiledOct. 50, 1962 15 Sheets-Sheet 8 INVENTOR. swam Fmza Q'wwamvms APPARATUSFOR FABRICATING SHEET METAL JOINTS Filed Oct. 30, 1962 E. C. FRAZE July27, 1965 15 Sheets-Sheet 9 OnP w INVENTOR. EflRL axis V2911 qw-vomawsJuly 27, 1965 E. c. FRAZE 3,196,817

APPARATUS FOR FABRICATING SHEET METAL JOINTS Filed Oct. 30, 1962 15Sheets-Sheet 10 Fuh- A INVENTOR.

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APPARATUS FOR FABRICATING SHEET METAL JOINTS Filed Oct. 30, 1962 15Sheets-Sheet 11' l N VEN TOR. Eva-m; Cm Fzwua.

3,196,817 APPARATUS FOR FABRIGATING SHEET METAL JOINTS Filed Oct. 30,1962 E. C. FRAZE July 27, 1965 15 Sheets-Sheet 12 INVENTOR. 11mm QJ-LonFERZE.

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APPARATUS FOR FABRICATING SHEET METAL JOINTS July 27, 1965 15Sheets-Sheet 13 Filed Oct. 30, 1962 I NVEN TOR. Eknfik. CLEO VER'LE.

QTY QRNEHB YRS-55 July 2%,]965 c. FRAZE 3,196,817

APPARATUS FOR FABRICA'IING SHEET METAL JOINTS Filed 001:. 30, 1962 15Sheets-Sheet 14 I NVEN TOR. EEMRL CLEO VY-QZE.

T T OYDAEYS E c. FRAZE 3, 7 APPARATUS FOR FABRICATING SHEET METAL JOINTSJuly 27, 1965 15 Sheets-Sheet 15 Filed 001:. 50, 1962 l NVEN TOR. Elna;m VLQZE BY 'twozgua United States Patent C) 3,196,817 APPARATUS FORFABRICATING SHEET METAL JOINTS Ernral Cleon Fraze, 355 W. Siroop Road,Dayton, Ohio Filed Set. 30, 1962, Ser. No. 234,107 Ciaims. (Cl. 113-4)This application is a continuation-in-part of my pending application,Serial No. 193,060, filed May 2, 1962, for Sheet Metal Joint and Methodand Means of Fabrication, now abandoned, which, in turn, in acontinuationin-part of my application, Serial No. 130,884, filed August11, 1961, now abandoned.

This invention relates to a high speed multiple-stage apparatus forattaching devices to sheets of deformable material, and, moreparticularly, is directed to such an apparatus that fabricates thejoints without using any fasteners whatsoever and without breaking thecontinuity of the sheets. While the invention is widely applicable forits purpose of attaching a member to a deformable sheet, it has specialutility for those applications in which the sheet of deformable materialis a fluid-confining wall. Since the continuity of the fluid-confiningwall is not broken, the invention eliminates the problem of making thejoint fluid-tight.

The invention has been initially embodied in an apparatus for the rapidcontinuous production of metal can tops that have manually removabletear strips whereby sealed cans incorporating the tops may be openedwithout the use of tools. This particular practice of the invention hasbeen selected by way of example for the purpose of the presentdisclosure and will provide adequate guidance for those skilled in theart who may have occasion to apply the underlying principles to otherspecific purposes.

lt is highly desirable to provide sealable cans, for example cans forfruit juices, beverages and various food products and articles subjectto deterioration by the atmosphere, with the can tops or end wallsscored to provide tear strips and with tabs attached to the tear stripsto serve as handles for severing the tear strips to permit the can topsor end walls to be removed without the use of a can opener or liketools.

The problem of attaching the tab to the tear strip of a can top in adependable manner without any possibility of incurring leakage at thejoint is solved by forming a small part of the sheet metal of the tearstrip into a hollow rivet element. The hollow sheet metal rivet elementis inserted into an aperture of the tab and is then deformed intopositive engagement with the tab. Since containers of this type must beproduced at exceedingly low cost, the pressing requirement is to providea completely automatic apparatus to convert blank can tops into finishedcan tops and simultaneously to produce the required tabs from sheetmetal stock. More specifically, the requirement is to provide a fullyautomatic apparatus capable of carrying out the sequence of steps at theoperating stations shown in the following flow chart:

3,196,817 Patented July 27, 1965 g"- Ce STA TION A Partially blank tab STA TI ON B Form ribs in tab STATION 1 Form a dimple in a blank STATION 0can top Punch aperture in tab S TA TI ON 2 STA TI ON D Form the dimpleinto a 1101- low rlvet element Coin radius in rim of tab aperture STA TION 8 STA TI ON E Score the can top to form the tear strip Sever tab STATI ON 4 Place the tab on the hollow rivet element and spread the hollowrivet element slightly to hold the tab in position STA TI ON 5 Deformthe hollow rivet element into permanent en gagement with the tab It willbe readily apparent to those skilled in the art that various well knowntypes of conveyor mechanisms may be used to advance the can tops bystages through the sequence of can top operations and at the same timesynchronously advance material for the tabs by stages through theseqeunce of tab operations. For example, a turntable may be used foreither or both of the sequences, the turntable being rotatedintermittently to carry the work in process from operating station tooperating station.

In the particular embodiment of the invention selected for the presentdisclosure, the can tops, blanked out and formed in advance, are fed toone end of a straight line conveyor to progress through the successiveoperating stations for the can tops. At the same time strip material forthe tabs progresses through a second series of operating stations in asecond straight line that intersects the first straight line at Station4 where the tabs and the can tops are brought together.

The conveyor system for the can tops comprises a series of workholderscarried by a pair of parallel continuous conveyor chains which moveintermittently to shift the workholders through Stations 1 to insequence. Each workholder carries two can tops and two sets of dies ateach station operate on the two can tops simultaneously. In the meantimea strip of metal for the tabs advances step by step through progressivedies to produce the required tabs for each successive pair of can topsarriving at Station 4.

As will be explained, the invention solves the problem of positioningthe workholders accurately at the different processing stations wherehigh precision is essential and solves all of the other problemsinvolved in carrying out both the can top cycle and the tab cycle athigh speed in a continuous automatic operation. These other problemsinclude: feeding the blank can tops to the workholder; safeguarding theapparatus from damage by faulty operation; operating the dies andconveyor chains in synchronism; indexing the conveyor chains foraccurate intermittent movement of the workholders from station tostation; using close fitting positioning jigs for the workholders whererequired without any possibility of the close fitting workholderssticking in the jigs; employing a progressive die for operating on asingle strip of metal to produce two tabs simultaneously spaced toarrive simultaneously at Station 4; transferring the finished tabs tothe can tops at Station 4; and discharging the finished can tops fromthe workholders at the end of the conveyor line.

The features and advantages of the invention may be understood from thefollowing detailed description and the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is a fragmentary perspective view of a can equipped with a tearstrip as produced by the present apparatus;

FIG. 2 is a plan view of a blank can top after the first step of forminga dimple;

FIG. 3 is a plan view of a can top after the second step of forming thedimple into a hollow rivet;

FIG. 4 is a plan view of a can top after the third step of scoring thecan top to form the tear strip;

FIG. 5 is a diagrammatic plan view showing how a tab is initially placedon the hollow rivet;

FIG. 6 is a plan view of the finished can top with the hollow rivetswaged into permanent connection with the tab;

FIGS. 7 to 11 are sectional views corresponding to adjacent FIGS. 2 to 6respectively, FIG. 7 being taken along the line 77 of FIG. 2, FIG. 8being taken along the line 8-8 of FIG. 3, FIG. 9 being taken along theline 99 of FIG. 4, FIG. 10 being taken along the line 1010 of FIG. 5 andFIG. 11 being taken along the line 1111 of FIG. 6;

FIG. 12 is an enlarged sectional view showing how dies cooperate atStation 1 to form a dimple in a blank can p;

FIG. 13 is a similar view showing how dies cooperate at Station 2 toform the dimple into a hollow rivet element;

FIG. 14 is a perspective view of the lower die in FIG. 13;

FIG. 15 is an enlarged fragmentary sectional view showing how the metalof a can top is scored at Station FIG. 16 is an enlarged sectional viewshowing how dies cooperate to spread the hollow rivet element slightlyinto temporary engagement with a tab at Station 4;

FIG. 17 is a similar view showing how dies cooperate at Station 5 toswage the hollow rivet element into permanent engagement with the tab;

FIG. 18 is a fragmentary sectional view showing how retractible fingersfunction to release blank can tops one at a time from a stack of cantops in a supply chute:

FIG. 19 is a simplified fragmentary elevational view showing a rack andeccentric assembly of the mechanism for actuating the fingers in FIG.18;

FIG. 20 (first sheet) is a perspective view of a workholder and adjacentportions of two associated conveyor chains for carrying pairs of cantops through Stations 1 to 5;

FIG. 20a is a fragmentary sectional view of a portion of a workhoidertaken along the line Zita-2.0a of FIG. 12 and showing the constructionof one of the retractible fingers for releasably holding a can top inthe workholder;

FIG. 21 is a sectional taken along the line 21-21 of FIG. 29 showing howeach successive workholder fits releasably into an accurate positioningjig at each of Stations 1 to 3;

FIG. 22 is a fragmentary sectional view showing how a shuttle platereciprocates lower rams at Stations 4 and 5;

FIG. 22:: is a perspective View of the shuttle plate of FIG. 22;

FIG. 22b is a fragmentary perspective view of a cam member that ismounted on the lower end of each of the lower rams in FIG. 22;

FIG. 23 is a fragmentary sectional view showing one of the threeyielding pawls that supports a stack of the finished can tops in adischarge chute;

FIG. 24 is a side elevational view of the selected embodiment of theapparatus;

FIG. 25 is an end elevation of the apparatus as seen along the line 2525of FIG. 13;

FIG. 26 is an enlarged transverse section along the line 2626 of FIG. 24showing the mechanism for feeding blank can tops to the successiveworltholders;

FIG. 27 is a horizontal section as seen from below along the line 27-27of FIG. 26 showing a portion of the mechanism for controlling theretractible fingers for feeding blank can tops to the successiveworkholders;

FIG. 28 is an enlarged fragmentary longitudinal section of the apparatusshowing one of the sets of dies at each of the Stations 1 to 3 FIG. 29is an enlarged transverse section along the line 23-29 of FIG 24 showingthe two sets of dies at Station 1;

FIG. 30 is a similar transverse section along the line 3)30 of FIG. 24showing the two sets of dies at Station FIG. 31 is a similar transversesection along the line g131 of FIG. 24 showing the two sets of dies atStation FIG. 32 is a horizontal section taken along the line 32-32 ofFIG. 24 as well as along line 32 32 of FIG. 33 showing the progressivedies for forming the tabs at Stations A to E;

FIG. 33 is a longitudinal section along the line 33-33 of FIG. 32showing the progressive dies at Stations A to E for forming the tabs;

FIG. 34 is a greatly enlarged portion of FIG. 33 showing a pair ofcooperating coining dies at Station D for rounding the edges of theaperture in a tab;

FIG. 35 is a sectional view along line 35-35 of FIG. 24 showing themechanism for transferring the finished can topsto two discharge chutesand also showing the mechanism for intermittently feeding strip materialto the progressive dies for forming the tabs;

FIG. 36 is a transverse section along the angular line 36-36 of FIG. 24showing the two lower rams at Station 4 and mechanism for actuating theshuttle plate to reciprocate the rams;

FIG. 37 is a longitudinal section along the line 3737 of FIG. 36 showingthe same mechanism and also showing the dies at Stations 4 and 5 andFIG. 38 is a fragmentary perspective view showing how a nipping die atStation E transfers a finished tab to a can top at Station 4.

The successive operations on the can tops and labs FIG. 1 shows a canwith a metal top, generally desig nated T, as produced by the apparatusof the present embodiment of the invention. The can top T is scoredalong a pair of lines to form a tear strip 42 in a spiral-like formationcircumscribing the periphery of the top so that removal of the tearstrip in effect severs the top from the can. The tear strip 42 has aleading end indicated at 44 in FIG. 4 and one end of a thin tab 45 of asuitable metal is attached to the leading end of the tear strip to serveas a handle for manual removal of the tear strip.

The tab 45 is normally positioned in face-to-face engagement with thecan top so that it does not interfere with normal stacking of the cansfor shipment or display. The tab 45 is formed with a plurality oflongitudinal ribs 48 to stiffen the tab and permit the tab to functionas a relatively rigid lever for prying the leading end of the tear stripfrom the can top. Thus lifting the tab by its free end causes itsopposite end to serve as a fulcrum for initiating the tearing action.

The tab 45 is formed with an aperture 59 as indicated in FIG. 5 toreceive a hollow rivet element 52 that is formed in the sheet metal ofthe leading end of the tear strip 42, the hollow rivet element beingbest shown in FIGS. 3 and 8. Preferably, the aperture 5%? is surroundedby an embossed rib 54 (FIGS. 16 and 17) which reinforces the rim of theaperture. It will be noted that both the aperture of the tab and thehollow rivet element 52 are of elongated or non-circular configuration.In the finished can top T shown in FIGS. 1 and 6, the hollow rivetelement 52 extends through the aperture 56 of the tab and is flattenedand swaged outwardly to form a rivet head as best shown in FlG. 17 forpermanent and positive engagement of the leading end of the tear stripwith the tab.

At Station 1, a relatively large circular dimple 56, shown in FIGS. 2and 7, is formed in the blank can top T by the pair of dies shown inFIG. 12 comprising an upper female die 58 with a circular recess 6t anda lower male die 62 having a suitably tapered nose 64. The lower maledie 62 is surrounded by a pressure pad 65 which clamps the metal of thecan top against the upper die 58 with sufiiciently light pressure topermit the sheet metal to creep radially inward towards the male die.The resulting dimple 56 which is much larger in area than thesubsequently formed hollow rivet element 52 is only slightly thinnerthan the surrounding sheet metal of the can top.

At Station 2, the dimple 56 is formed into the hollow rivet element 52by die means shown in FIGS. 13 and 14 comprising an upper female die 66and a lower male die 68. The upper female die 66 has a cavity 70 and aleading face '72 and is surrounded by a pressure pad '74. The pressurepad 74 is under sufficient spring pressure to cooperate with a lower dieblock 75 to resist creepage of the sheet metal of the can top radiallyoutward from the female die 66. The cavity 70 which is of the elongatedcross-sectional configuration of the desired hollow rivet element 52 isdimensioned in depth to avoid restraining the upper surface of thetransverse wall 76 that forms the top or outer end of the hollow rivetelement 52.

The lower male die 68 serves as a forming mandrel so that when the twodies 66 and 68 close together they convert the relatively large dimple56 into the smaller steepshouldered hollow rivet element 52, the sidewalls of the rivet element being substantially perpendicular to theplane of the can top.

In the forming operation the two dies 66 and 63 function somewhat in themanner of conventional shrink dies to cause the metal of the previouslyformed dimple 56 to flow radially inward to result in thickening of thecentral portion of the dimple that is not restrained by the telescopingdie surfaces. Thus the transverse wall '76 of a hollow rivet element 52is increased in thickness as indit5 cated in FIG. 13, the thickness inthis instance being substantially equal to the thickness of the tab 45.

At Station 3 an upper die '73 shown in FIG. 15 cooperates with a lowerdie 80, the upper die including a scoring element 82 to thin the metalof the can top along the pair of lines at) to form the desired tearstrip 42. The lower die 34 serves as an anvil with a fiat upper surfaceto support the can top against the action of the scoring element 82. Ifthe thickness of the can top T is of the order of 0.008 inch thick, themetal may be scored to a depth of 0.005 inch. At the same station, theupper die 73 cooperates with the lower die to offset a portion of thesheet metal of the can top downward to form an elongated recess in theupper surface of the can top, which recess is designated 84 in FIG. 4.The parallel side walls of the recess 84 stiffen the sheet metal of thecan top locally to facilitate the initial separation of the leading endof the tear strip from the can top by the leverage of the tab 45.

At Station 4 where a finished tab 45 is placed on the hollow rivetelement 52 as indicated in FIG. 5, an upper nipping die 88 which seversa finished tab from a metal strip carries the finished tab downward toplace the tab on the hollow rivet element 52. As best shown in FIG. 16,a can top T at Station 4 rests on a lower die block 85 which surroundsan upwardly protruding anvil member 86 that is dimensioned to fit snuglyinto the hollow rivet element 52. The upper nipping die 83 in FIG. 16 iscut away to conform to the embossed rib 5 of the tab 45 and incorporatesa central ram member 90 that cooperates with the lower anvil member 86to spread the rivet element 52 slightly in all radial directions forlight engagement with the tab 45 to hold the tab in place as the can topis conveyed to Station 5.

At Station 5 the can top T with the tab 45 lightly engaged therewith isprocessed by a pair of dies in the manner indicated in FIG. 17. In FIG.17 the can top T rests on a lower die block 92 that incorporates ananvil member 94 that protrudes upward into the interior of the hollowrivet element 52 in abutment with the inner surface of the transversewall 7% of the hollow rivet. An upper die block 55 in FIG. 17 is cutaway to clear the embossed rib 54 of the tab 45 and incorporates anupper ram member 96 to cooperate with the lower anvil member 9 forswaging the hollow rivet element 52 radially in all directions. Theupper ram member 96 is driven forcibly against the transverse wall 76 ofthe rivet element 52 to squeeze and force the metal of the transversewall outwardly by extrusion to form the previously mentioned rivet head55 for firmly uniting the tab with the can top. Since the height of thehollow rivet element 52 is somewhat greater than the thickness of thetab 45 the die operation also tends to here the side wall of the hollowrivet element 52 radially in all directions to force the side wall ofthe rivet element into pressural engagement with the outer rim of theaperture 50 of the tab. Preferably so-much of the metal of thetransverse wall 76 of the hollow rivet element is displaced radially byextrusion that the resultant peripheral bead or rivet head 55 is thickerthan the final thickness of the transverse wall. Thus at Station 5 thecan top is completed to provide the finished can top shown in FIGS. 6and 11.

With reference to the fabrication of the tabs 45, a narrow strip ofmetal 98 is fed into the apparatus transversely thereof in the mannerindicated in FIG. 35 and is processed by progressive dies at Stations Ato E which are indicated by corresponding letters in FIGS. 32 and 33. AtStation A spaced dies partially blank out two tabs 45 simultaneouslyleaving the two tabs connected to the metal strip 98 by narrow tonguesso that the metal strip may serve as means to transport the tabs to theremaining Stations C to E in sequence.

At Station C the apertures 50 are punched in the tabs and at Station Dthe rims of the apertures 50 are coined or rounded. At Station E thepreviously mentioned nip- '2 ping dies 88 complete the blankingoperation to sever the finish-ed tabs from the metal strip and at thisstation the nipping dies carry the finished tabs downward to thepreviously mentioned Station 4 and serve as die means at Station 4 forlightly spreading the hollowurivet elements 52 into light or temporaryengagement with the tabs.

General description of the apparatus As shown in FIG. 24, the frameworkof the apparatus includes a base structure, generally designated 1%,four columns 162 extending upward from the base structure to supportfixed structure associated with Stations 1 to 3 for processing the cantops and four additional columns 1M extending upward for supporting thefour corners of fixed structure associated with Stations 4 and 5 forprocessing the can tops and associated with Stations A to E forprocessing the tabs.

For the purpose of moving can tops in pairs firom a feed station under apair of 'feed chutes 105 through Stations 1 to 5 to a discharge stationunder a pair of discharge chutes 106, a series of dual workholders 111of the construction shown in FIG. 20 are mounted at evenly spaced pointson a pair of parallel conveyor chains 112. An upper run of the twoconveyor chains extending from a pair of upper sprockets 114 to a pairof upper sprockets 115 forms a straight conveyor line through Stations 1to 5, the return run of the two continuous conveyor chains extendingfrom a lower pair of sprockets 116 to a cooperating lower pair ofsprockets 113.

As shown in FIG. 20, each of the workholders 111 may be in the form of arelatively heavy rectangular plate with two circular apertures 120formed with circumferential ledges or flanges 122 to serve as seats fora pair of the can tops. Each of the circular seats 120 18 provided witha plurality of circumferentially spaced spring-loaded fingers 124 whichserve the purpose of yieldingly retaining the can tops in the seatsduring the operations at Stations 1 to 5. The blank can tops are forcedinto the circular seats 120 at the feed station and are forced upwardout of the seats at the discharge station. The operating Stations 1 to 5are spaced five inches apart measured from center to center and the twoconveyor chains are intermittently moved five inches to move the cantops to the five stations in succession.

At Stations 1 to 3 the upper dies of the previously mentioned die setsare fixedly mounted on an upper platen 125 that is supported by the tourcolumns 162 and the corresponding lower dies are mounted on a lowerreciprocative platen 126 that is slidingly guided by the four columns.At Stations 4 and 5 the previously described lower dies are mounted onupwardly extending rams comprising a pair of rams 128 (FIG. 36) forStation 4 and a similar pair of rams 130 (FIG. 37) for Station 5. Theupper dies at Stations 4 and 5, as well as the upper d es at Stations Ato E are mounted on an upper reciprocative platen 132 which is slidinglyguided by the upper ends of the four columns 104. The lowerreciprocative platen 126 for Stations 1 to 3 and the upper reciprocativeplaten 132 for Stations 4 and 5 and for Stations A to E are all actuatedby a lower drive shaft 134 that extends longitudinally of the apparatus.

As shown in FIG. 24, a first sensing means in the form of a pair ofphotoelectric devices 135 is positioned between the feed station andStation 1 to sense whether or not a traveling workholder has an emptyseat, a second sensing means 136 of the same character is positionedbetween Stations 3 and 4 for the same purpose and a third sensing means138 in the form of a pair of microswitches is located between Station 5and the discharge station at the chutes 106 to detect whether or nottabs are assembled to the can tops as they approach the dischargechutes. If either of the first two sensing means detects that aworkholder i110 lacks a can top or if the third sensing means ascertainsthat a tab is missing rom a can top, the drive shaft 134 is immediatelystopped.

All of the upper dies for progressively forming the tabs at Stations Ato E are mounted on the reciprocative upper platen 132 as shown in FIG.33 and the lower dies for these stations are mounted on fixed structurebetween the lower rams 128 and and the upper reciprocative platen 132.

The metal strip 98 for forming the tabs 45 is supplied in a large rolland is fed intermittently to the apparatus in a well known manner by themechanism shown in FIG. 35. An upper idler roller 14!) under pressurefrom a coil spring 142 cooperates with a lower drive roller 144 that isdriven at a constant speed by an individual motor (not shown). The driveroller 144 is journalled on an eccentric member (not shown) having anarm 145 for oscillation to move the drive roller into and out of drivingcontact with th underside of the metal strip 98. Thus the drive roller144 periodically drives the metal strip by periodic upward pressureagainst the metal strip in opposition to the pressure of the idlerroller 140.

The operating arm 145 is connected by a link 146 to a lever 148 thatrocks on a central fulcrum 150. The lever 148 is connected by aconnecting rod 152 to a crank 154 on a sprocket 155, the sprocket 155being driven from a sprocket 156 (FIGS. 24 and 35) on the drive shaft134 by means of a sprocket chain 158. The radial position of the crank154 on the sprocket 155 is adjustable to adjust the throw of the crankand thereby adjust the length of the metal strip 98 that is advancedinto the apparatus for each rotation of the drive shaft 134. FIGS. 24and 35 also show a second sprocket 160 on the drive shaft 134 whichdrives a pump 162 by means of a sprocket chain 164 for circulatinglubricant throughout the apparatus.

Considering the length of the metal strip 98 as divided into steps justlong enough for blanking out one tab 45, the crank 154 is adjusted onthe sprocket 155 for the drive roller 144 to advance the metal strip twosteps on each of the revolutions of the drive shaft 134 that causesreciprocation of the various dies. Referring to FIG. 33, two upperpunches 165 at Station A for partially blanking the tabs out of themetal strip 98 are two steps apart, i.e., considering the first of thetwo upper punches as operating on the first step along the length of themetal strip 98, the second punch operates on the fourth step. At StationB two sets of dies for forming ribs 48 on the tabs operate on twocontiguous steps along the length of the metal strip 9 8. In like mannerthe dies at Station C for punching the apertures 50 in the tabs and thedies at Station D for coining or rounding the rims of the apertures 50operate on two contiguous steps of the metal strip. The two nipping dies83 at Station E are spaced apart with six intervening steps, the twonipping dies being thus spaced apart by the distance between the twohollow rivet elements 52 on the two can tops respectively on theworkholder at Station 4. Pilot holes 166 (FIG. 32) are punched in themetal strip 93 at Station A to be used by suitable pilot pins (notshown) for accurately registering the metal strip with the dies at theremaining Stations B to E.

With the described arrangement of the progressive tab fabricating dies,finished tabs are punched out of all of the successive steps of themetal strip 98. Beyond Station E the remaining material of the metalstrip is cut away two steps at a time by a punch 167 (FIGS. 33 and 36)and the pieces of scrap fall through an inclined chute 168 to a scrapbox (not shown).

The mechanism for actuating the various dies As shown in FIGS. 24 and25, the drive shaft 134 which is journalled in suitable bearings 170 isdriven by a variable specd motor 172 through the medium of a belt 174and what is known commercially as a Fawick Fly Wheel Drive whichincludes a fly wheel 175 and an assembly comprising an air brake 176 anda clutch 173. The fly wheel 17 5 and the air brake-clutch assembly aremounted on the drive shaft 134 with an inclined link 180 (FIG. 25)

9 anchoring the brake shoes (not shown). Upon receiving a signal fromany one of the three sensing means 135, 136 and 138, the clutch 178 isdisengaged to relase the drive shaft 134 from the fly wheel 175 and theair brake 176 is simultaneously actuated to bring the drive shaft to aninstant stop.

Referring again to FIG. 24, the reciprocative lower platen 125 forStations 1 to 3 is operated in a well known manner by two spacedeccentric assemblies 182 on the drive shaft 134 the reciprocative platenbeing connected to the two eccentric assemblies by two correspondingconnecting rods 184 which pivot on a cross pin 185 of the platen.

To actuate the upper reciprocative platen 132 an overhead walking beam185 is fulcrumed by a pivot 183 on fixed structure above the fixedplaten 125 and is actuated by a yoke 1% which functions in the manner ofa pull rod. As shown in FIG. 35 the upper end of the yoke 19% isconnected to the walking beam 186 by pivot means 192 and its lower endis pivotally connected by a cross pin 1% to an eccentric assembly 195 onthe drive shaft 134. The reciprocative platen 132 is operativelyconnected to the beam 126 by a pair of connecting rods 1% (FIGS. 24 and35), the upper end of each connecting rod being pivotally connected tothe walking beam by a corresponding pin 197 and the lower end of eachconnecting rod being connected to the platen 132 by a ball joint 1%. Asmay be seen in FIG. 35, the yoke 190 straddles the upper runs of the twoconveyor chains that carry the workholders 110 so that the yoke exertsbalanced downward pressure on the die sets at Stations '4 and 5.

Referring again to FIG. 24 an intermittent drive means or indexer,generally designated 2%, drives a shaft 292 carrying the two previouslymentioned sprockets 114 for intermittently advancing the two conveyorchains 112 by increments of five inches on each revolution of the maindrive shaft 134. The indexer 206 may be what is known commercially as aFerguson Drive and may be driven by means of three sprocket chains 2114which connect three corrsponding sprockets 205 on the drive shaft 134with three sprockets 2% on the indexer.

The two lower rams 128 and 130 at Stations 4 and 5 respectively, areactuated by a drive means shown in FIGS. 22, 22a, 22b, 36 and 37. Anupright lever 2117 mounted on a central fulcrum 263 is oscillated by theupper reciprocative platen 132. For this purpose the upper end of thelever carries a follower 2119 in the form of a roller that rides in anangular cam slot 216 that moves with the platen 13-2. The lower end ofthe upright lever 2117 is connected by a short link 2111 with a shuttleplate 212. By this arrangement the shuttle plate 212 makes onereciprocation for each reciprocation of the upper platen 132.

Each of the four lower rams 123, 1311 has an inclined cam surface 213 onits lower end and each ram is provided on its lower end with adownwardly extending axial belt 214 of stepped configuration whichmounts a narrow cam block 215 on the lower end of the ram. As shown inFIG. 22b, each of the cam blocks 215 is formed with a pair of inclinedcam surfaces 216 on its opposite sides respectively. Preferably suitablecompression springs 21'? (FIG. 36) act on the four bolts 214 to urge thefour lower rams downward.

As shown in FIGS. 22a and 36 the shuttle plate 212 has a longitudinalslot 218 that straddles the cam blocks 215 of the two lower rams 128 anda second similar slot 219 that straddles the cam blocks 215 of the twolower rams 13%. The shuttle plate 212 has two transverse inclined camsurfaces 2211 and 221 on its upper side to cooperate with the camsurfaces 213 of the four lower rams to lift the rams when the shuttleplate is moved to the right as viewed in FIGS. 22, 22a and 36. In likemanner, the underside of the shuttle plate 212 is formed with twotransverse inclined cam surfaces 222 and 223 to contact the inclined camsurfaces 216 of the four cam blocks 215 to to lower the four rams withthe assistance of the four compression springs 217.

The workholders and their operation As best shown in FIG. 20 each of therectangular workholders that is carried by the pair of parallel conveyorchains 112 is mounted on skids 231) at its opposite ends respectively.Each of the two skids 230 is recessed as shown at its opposite ends forengagement and retention in a loose manner by two pairs of pins 232 thatextend laterally from the two conveyor chains 112 respectively. By thisarrangement the various workholders are held captive by the two conveyorchains but have substantial freedom for movement relative to the chainsto permit the workholders to be lifted into operating positions atStations 1 to 5.

As may be seen in FIG. 26 the opposite ends of the workholders 111i reston the two conveyor chains 112 and the two conveyor chains in turn ridealong parallel rails 23 1 as the workholders shift from station. On thereturn run of the two conveyor chains at the bottom of the apparatus theinverted workholders 110 ride along fixed rails 235 as shown in FIG. 25and the two conveyor chains ride on two corresponding fixed rails 236.

Referring to FIGS. 20 and 20a, a ring 233 is mounted around the rim ofeach of the circular seats to guide the blank can tops into the seats,each of the rings being tapered to form an inner circumferential guidesurface 246. Each of the springloaded fingers 124 is mounted in a radialguideway 242 under the ring 238 and is formed with a retaining pin 244that extends upward through a corresponding short radial slot 245 in thering. In the absence of a can top in a circular seat 120 of a workholder110, the fingers 124 are held at their radially inward limit positionsby a garter spring 246 that is common to all three of the fingers. Whena can top '1 is forced downwardly into a circular seat 120 of aworkholder 116 the rim of the can top is guided by the guide surface24-19 of the ring 238 to make contact with inclinded cam surfaces 248 atthe ends of the fingers 124. The can tops T act on the cam surfaces 248to retract the three fingers 124 and then drop below the cam surfaces tobe frictionally retained in the workholder seat by the fingers 124 underthe pressure exerted by the garter spring 246. Thus the blank can tops Tmay be mounted on the successive workholders 110 by merely forcing thecan tops downward to seat on the inner circumferential ledges 122 of theworkholders.

At each of the Stations 1 to 5, the successive workholders 110 arelifted from the two conveyor chains 112 into seats that locate theworkholder accurately relative to the dies at the station. At Stations 1to 3 where exceedingly high accuracy is required in the positioning ofthe can tops, high precision jigs receive the workholders with closefit.

As shown, for example, in FIG. 31 illustrating Station 3, each of thepositioning jigs includes an upper rectangular base plate 252 which isattached to the upper reciprocative platen 125. Two downwardly extendingjig arms 2541 at the opposite ends of the base plate 252 are spacedapart to confine with close fit the opposite ends of the successiveworkholders 110. In like manner as indicated in FIG. 21, two pairs ofjig arms 255 extending downward from the base plate 252 make close fitwith the opposite longitudinal sides of each successive workholder 119.The lower end of each of the six downwardly extending jig arms is cutaway as shown in FIG. 31, to form a shoulder 256 for abutting the uppersurface of a workohlder and to form an adjacent shoulder 258- to fitagainst the edge of the workholder so that the six jig arms cooperate toform an accurately dimensioned and closely fitted rectangular jig seat.The lower end of each of the six downwardly extending jig arms 254 and255 is additionally tapered as shown at 260 to guide the successiveworkholders into the jig seat.

1. IN AN APPARATUS OF THE CHARACTER DESCRIBED FOR FORMING A HOLLOW RIVETIN A SHEET-LIKE MEMBER TO SERVE AS MEANS FOR ATTACHING THE SHEET-LIKEMEMBR TO AN APERTURE OBJECT, THE COMBINATION OF: MEANS TO ADVANCE THEMEMBER THROUGH A SEQUENCE OF OPERATING STATIONS; A FIRST FORMING MEANSAT ONE OF SAID STATIONS TO FORM A DIMPLE IN SAID MEMBER; A FIRST HOLDINGMEANS AT SAID ONE STATION HOLD THE MEMBER DURING THE DIMPLE-FORMINGOPERATION AND TO PERMIT SLIPPAGE OF THE MATERIAL OF THE MEMBER RADIALLYINWARDLY TOWARD THE DIMPLE AREA TO MINIMIZE THINNING OF THE MATERIAL INTHE DIMPLE-FORMING AREA; A SECOND FORMING MEANS AT A SUBSEQUENT STATIONTO SHRINK SAID DIMPLE INTO A HOLLOW RIVET HAVING A TRANSVERSE WALL OFSUBSTANTIALLY SMALLER AREA THAN THE DIMPLE WITHOUT PRESSURE ON THE AREAOF THE TRANSVERSE WALL; AND A SECOND HOLDING MEANS AT SAID SUBSEQUENTSTATION TO SURROUND THE DIMPLE AREA TO CLAMP THE MEMBER UNDER PRESSUREDURING THE SHRINKING OPERATION TO PREVENT SLIPPAGE OF THE MATERIALRADIALLY OUTWARD AWAY FROM THE DIMPLE AREA TO PROMOTE THICKENING OF THEMATERIAL OF THE HOLLOW RIVET IN THE AREA OF SAID TRANSVERSE WALL.